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A collection of 1149 otoliths of the Ypresian and Ypresian–Lutetian transition (early Eocene) from 18 sites across five states in the eastern and southern regions of the USA was analyzed. In total, 33 otolith-based taxa are documented, of which 27 are identified at the species level. Nine of these are introduced as new species: “Conger” biaculeatus sp. nov., Bauzaia gibbosa sp. nov., Ampheristus brevicaudatus sp. nov., Symmetrosulcus virginicus sp. nov., Neobythites longesulcatus sp. nov., “Neobythites” pamunkeyensis sp. nov., “Neobythites” stringeri sp. nov., Waitakia dorsogibbosa sp. nov., and “Haemulon” ypresiensis sp. nov. The assemblages are distinct when compared to their younger Eocene counterparts in America. This distinction is primarily characterized by the high proportion of the newly introduced species or exclusive Ypresian species. Additionally, we highlight the presence of 10 amphi-Atlantic species originally described in European deposits. Significantly, the composition of the otolith collection supports the interpretation of a shallow-water environment for the sampled sites during the Ypresian. This ecological setting appears to persist into the subsequent middle and late Eocene within the same geographic region.

The fossil otoliths of the southern USA have been known for more than 130 years and are among the richest assemblages worldwide. However, previous studies are often scattered and with outdated systematic scheme. A collection of over 25000 otoliths ranging in age from the Lutetian to the Priabonian from 47 sites in five states in the eastern and southern USA is analysed here. Combined with the earlier described material, at least 101 otolith-based taxa are documented, of which 83 are identified at species level. Fourteen of these are introduced as new species: Elopothrissus bernardlemorti sp. nov., “Muraenesox” barrytownensis sp. nov., Pseudophichthys texanus sp. nov., Paraconger wechesensis sp. nov., Neoopisthopterus weltoni sp. nov., “aff. Glyptophidium” stringeri sp. nov., Symmetrosulcus dockeryi sp. nov., Mene garviei sp. nov., “Citharus” varians sp. nov., Waitakia beelzebub sp. nov., Astroscopus compactus sp. nov., Parascombrops yanceyi sp. nov., Anisotremus rambo sp. nov., and Pagellus pamunkeyensis sp. nov. The assemblages are distinct fom contemporary European faunas by the complete lack of mesopelagic fish otoliths, and by the presence of sciaenids. Dominant taxa in the American Eocene are the Ophidiidae, Sciaenidae, Lactariidae, and Congridae. They indicate shallow-water environments for all the sampled sites. The notable abundance of those taxa suggests that they could have a higher turnover rate, and provided fundamental nutrition in the local Paleogene marine ecosystem. Further analyses of the species in the stratigraphic succession revealed that a faunal turnover between the Claiborne and Jackson seas was evident in teleosts, and it might be more widespread in other marine organisms in the region.

The Tortonian fish otoliths of northern Italy have been studied for more than a century and represent one of the best known otolith-based teleost faunas in the Miocene of the Mediterranean Basin. Yet with the growing knowledge on Recent otoliths, an updated taxonomic overview of this fauna is needed. Moreover, new material from hemipelagic Tortonian marls sampled at nine localities is described herein, revealing 109 taxa of which 88 are recognised at species level. Four of these are new: Coryphaenoides biobtusus sp. nov., “Merluccius” rattazzii sp. nov., Neobythites auriculatus sp. nov. and Lesueurigobius stironensis sp. nov. The compilation of previously studied and newly acquired material revealed a total of 118 nominal Tortonian species. At generic level, the fauna is characterised by many modern forms; more than 90% can be assigned to present day genera. At species level, however, more than half of the represented taxa are extinct. Based on the fossil otolith record, the Tortonian fauna of the Mediterranean is most similar to that of the Langhian (Badenian) of the Central Paratethys by sharing many extinct Miocene species, but it is also very close to that of the Pliocene Mediterranean, by sharing many modern Atlantic-Mediterranean forms. The Tortonian fauna is further characterised by many species that are apparently confined to the upper Miocene, resulting in a unique combination of its taxonomic composition.